Impact of Environmental Factors on the ACL Injury Risk in Recreational Alpine Skiing.

In recreational alpine skiing, an ACL injury represents the most common injury. Skiing is a complex activity where the skier interacts with the environment, such as weather, snow conditions, temperature, etc. Thus, the aim of this study was to evaluate the potential impact of environmental factors on ACL injury risk in recreational alpine skiers. Among a cohort of 392 ACL-injured skiers and 392 uninjured controls matched for sex and skiing skill, environmental factors were collected by questionnaire. Factors included weather conditions, snow conditions, perceived temperature, and slope difficulty at the time-point of the accident (ACL-injured skiers) or of questioning during the ski day (uninjured controls).Multiple logistic regression revealed that in addition to age, five environmental factors were significantly predictive of an ACL injury: fresh snow (OR 10.5), grippy snow (OR 7.8), icy slope condition (OR 12.4), very cold/cold perceived temperature (OR 1.6), and skiing on easy slopes (OR 6.9). In conclusion, besides age, environmental factors such as fresh and grippy snow, icy slope conditions, low temperatures, and flat slopes are associated with an increased ACL injury risk in recreational alpine skiing. Those factors are at least partly modifiable and should be taken into consideration for preventive strategies.

Impact of ski geometry data and standing height ratio on the ACL injury risk and its use for prevention in recreational skiers.

OBJECTIVES: To evaluate the impact of ski geometry data and standing height ratio on anterior cruciate ligament (ACL) injury risk of male and female recreational skiers. METHODS: A retrospective questionnaire-based, case-control study of ACL-injured and uninjured recreational skiers was conducted during six consecutive winter seasons. Ski geometry data (ski length, side-cut radius, widths of the tip, waist and tail) were recorded from each participant's skis. Standing heights at the front and rear components of the ski binding were measured with a digital sliding calliper, and the standing height ratio between the front and rear was calculated. RESULTS: A total of 1817 recreational skiers participated in this study, of whom 392 (21.6%) sustained an ACL injury. Multiple logistic regression analysis indicates a higher age, a lower skill level and riskier behaviour as independent individual risk factors associated with an ACL injury. An increase in ski length, tip width of the ski, standing height at the rear ski binding component, and in standing height ratio were found to be independent equipment-related risk factors for an ACL injury. CONCLUSION: Reduced ski length, narrower ski tip width, lower rear standing height and a lower standing height ratio (ie, rear component of the ski binding is more elevated compared with the front component) were associated with a reduced likelihood for ACL injury. When buying or renting skis, these parameters could be considered to reduce the likelihood of ACL injury in recreational skiers.

Ski-geometric parameters do not differ between ACL injury mechanisms in recreational alpine skiing.

PURPOSE: It is not known so far if ski-equipment-related factors differ between the ACL injury mechanisms, potentially influencing the circumstances and causes of falling, finally resulting in ACL injury. More specifically focusing on the injury mechanisms will provide a deeper understanding of injury causation. The aim of the study was to evaluate whether ACL injury mechanisms in recreational alpine skiing differ with regard to ski-geometric parameters, self-reported circumstances and causes of accident and injury severity. METHODS: Among a cohort of 392 ACL-injured (57.9% females) skiers, age, sex, height, weight, skill level, risk-taking behavior, circumstances and causes of accident, and ACL injury severity were collected by questionnaire. Additionally, patients had to recall their type of fall (ACL injury mechanism) by classifying forward and backward falls with and without body rotation. Ski length, side cut radius and widths of the tip, waist and tail were directly notated from the ski. RESULTS: The forward fall with body rotation was the most common reported ACL injury mechanism (63%). A riskier behavior was associated with forward falls without body rotation. Ski-geometric parameters did not significantly influence the type of ACL injury mechanism. Regarding accident characteristics, catching an edge of the ski was more frequent (p < 0.001) the cause for forward falls (75% and 67%) when compared to the backward falls (46 and 15%) and executing a turn was the most frequent action in all falls (39-68%). A complete rupture of the ACL (66-70%) was more commonly reported than a partial tear (30-34%) among all four non-contact ACL injury mechanisms (n.s.). CONCLUSION: In contrast to risk-taking behavior and accident characteristics, ski-geometric parameters and injury severity do not significantly differ between ACL injury mechanisms in recreational skiing. Thus, an individual skiing style seems to have more impact on ACL injury mechanisms than ski equipment. Future studies should evaluate potential effects of ski geometry on the incidence of ACL injury. LEVEL OF EVIDENCE: III.

In recreational alpine skiing, the ACL is predominantly injured in all knee injuries needing hospitalisation.

PURPOSE: The knee joint still represents the most frequent anatomical injury location accounting for about one-third of all injuries in recreational alpine skiers. However, comprehensive information on current knee injury patterns in this populations is sparse. METHODS: During the winter seasons 2016/17 and 2019/20, this retrospective questionnaire-based study was conducted in an Austrian sportclinic situated in a large ski area. Among a cohort of 282 recreational skiers (51.8% females), all injuries were diagnosed by the use of magnetic resonance imaging. Additionally, data were recorded on anthropometric characteristics, the perceived speed at the moment of injury, type of fall, physical fitness, self-reported skill level and risk-taking behaviour. RESULTS: The anterior cruciate ligament (ACL) was injured in all knee injuries recorded. Of the total study sample, 64.5% (n = 182) were ACL injuries with concomitant injuries and about 35.5% (n = 100) were isolated ACL injuries, not involving any other structures of the knee joint. In general, most common concomitant injury diagnoses among ACL-injured recreational alpine skiers were injuries of the medial collateral ligament (MCL) (n = 92, 50.5%), medial meniscus (MM) (n = 73, 40.1%) and lateral collateral ligament (LCL) (n = 41, 22.5%). No significant differences regarding additionally recorded characteristics were found between ACL-injured individuals with concomitant injuries and those with isolated ACL injury. CONCLUSIONS: Whereas, before the introduction of carving skis, the MCL was reported being the most common injured part of the knee, currently, the majority of knee injuries are ACL injuries accompanied by injury of other knee joint structures, i.e. the MCL, MM and LCL. LEVEL OF EVIDENCE: Level III.

Is ski boot sole abrasion a potential ACL injury risk factor for male and female recreational skiers?

OBJECTIVES: To evaluate the potential impact of ski boot sole abrasion on the ACL injury risk of recreational skiers. METHODS: During the past two winter seasons 2016/17 and 2017/18, this retrospective case-control study was conducted in one Austrian ski area. Among a cohort of 148 ACL-injured (51.4% females) and 455 uninjured recreational skiers (43.3% females), age, sex, height, weight, and self-reported skill level were collected by questionnaire, ski length and sidecut radius were notated and sole abrasion of the toe and heel piece of the ski boot was measured using a digital caliper. RESULTS: ACL-injured skiers showed a higher proportion of female (51.4% vs 43.3%, P < 0.001) and less skilled skiers (48.6% vs 20.9%, P < 0.001), and ski length to height ratio was higher (94.7 ± 3.7 vs 93.8 ± 5.0%, P = 0.019) compared to uninjured skiers. ACL-injured skiers used ski boots of greater abrasion at the toe (4.8 ± 1.8 vs 2.4 ± 2.5 mm, P < 0.001) and heel piece (5.4 ± 1.8 vs 3.3 ± 2.3 mm, P < 0.001) compared to controls. Multivariate regression analysis revealed, beside female sex (OR 6.0, 95% CI, 3.1-11.5, P < 0.001), lower skill level (OR 3.2, 95% CI, 1.9-5.4, P < 0.001) and ski length to height ratio (OR 1.1, 95% CI, 1.0-1.2, P < 0.001), sole abrasion at the toe (OR 1.8, 95% CI, 1.5-2.1, P < 0.001) and heel piece (OR 1.4, 95% CI, 1.2-1.6, P < 0.001) to be independently associated with an ACL injury among recreational alpine skiers. CONCLUSIONS: Based on the underlying findings, ski boot sole abrasion was found to be an independent risk factor and may contribute to an increased ACL injury risk.

Prevalence and potential risk factors of flight-related neck, shoulder and low back pain among helicopter pilots and crewmembers: a questionnaire-based study.

BACKGROUND: Flight-related neck, shoulder and low back pain are the most common musculoskeletal disorders among helicopter pilots and their crewmembers, thus becoming a growing concern. Information on the combined prevalence of these types of pain and related risks are scarce. The aim of this study was therefore to estimate pain prevalence and to evaluate potential risk factors for neck pain among helicopter pilots and crewmembers within the armed forces, the airborne police and airborne rescue organizations in Austria. METHODS: Among a cohort of 104 helicopter pilots and 117 crewmembers (69.8% compliance), demographics, flying experience, use of Night Vision Goggles (NVG), helicopter type flown, prevalence and intensity of musculoskeletal symptoms (pain was defined as any reported pain experience, ache or discomfort) were collected by an online-based questionnaire. RESULTS: For helicopter pilots the 12-month prevalence of neck pain was 67.3%, followed by low back (48.1%) and shoulder pain (43.3%). Among crewmembers, the 12-month pain prevalence were 45.3, 36.8 and 30.8% among the neck, lower back and shoulder, respectively. During this period, 41.8% of these helicopter pilots had experienced 8-30 pain days in the areas of neck (45.7%), shoulder (37.8%) and lower back (42.0%) whereas 47.8% of crewmembers self-reported 1-7 days of neck (54.7%), low back (44.2%) and shoulder (44.4%) pain in the previous year. The 3-month prevalence of neck pain was 64.4% followed by low back (42.3%) and shoulder pain (38.5%) for helicopter pilots. Among crewmembers, 41.9% suffered from neck, 29.9% from low back and 29.1% from shoulder pain the previous 3 months. Multivariate regression analysis revealed NVG use (OR 1.9, 95% CI, 1.06-3.50, p = 0.032), shoulder pain (OR 4.9, 95% CI, 2.48-9.55, p < 0.001) and low back pain (OR 2.3, 95% CI, 1.21-4.31, p = 0.011) to be significantly associated with neck pain. CONCLUSIONS: The 12- and 3-month prevalence of neck, shoulder and low back is considerably high among both, helicopter pilots and crewmembers confirming the existence of this growing concern. The use of NVG devices, shoulder and low back pain in the previous 12 months represent independent risk factors for neck pain. These findings highlight the need for longitudinal studies.

A spontaneous mutation in MutL-Homolog 3 (HvMLH3) affects synapsis and crossover resolution in the barley desynaptic mutant des10.

Although meiosis is evolutionarily conserved, many of the underlying mechanisms show species-specific differences. These are poorly understood in large genome plant species such as barley (Hordeum vulgare) where meiotic recombination is very heavily skewed to the ends of chromosomes. The characterization of mutant lines can help elucidate how recombination is controlled. We used a combination of genetic segregation analysis, cytogenetics, immunocytology and 3D imaging to genetically map and characterize the barley meiotic mutant DESYNAPTIC 10 (des10). We identified a spontaneous exonic deletion in the orthologue of MutL-Homolog 3 (HvMlh3) as the causal lesion. Compared with wild-type, des10 mutants exhibit reduced recombination and fewer chiasmata, resulting in the loss of obligate crossovers and leading to chromosome mis-segregation. Using 3D structured illumination microscopy (3D-SIM), we observed that normal synapsis progression was also disrupted in des10, a phenotype that was not evident with standard confocal microscopy and that has not been reported with Mlh3 knockout mutants in Arabidopsis. Our data provide new insights on the interplay between synapsis and recombination in barley and highlight the need for detailed studies of meiosis in nonmodel species. This study also confirms the importance of early stages of prophase I for the control of recombination in large genome cereals.

The evolution of structured illumination microscopy in studies of HIV.

The resolution limit of conventional light microscopy has proven to be limiting for many biological structures such as viruses including Human immunodeficiency virus (HIV). Individual HIV virions are impossible to study using confocal microscopy as they are well below the 200 nm resolution limit of conventional light microscopes. Structured illumination microscopy (SIM) allows a twofold enhancement in image resolution compared to standard widefield illumination and so provides an excellent tool for study of HIV. Viral capsids (CAs) vary between 110 and 146 nm so this study challenges the performance of SIM microscopes. SIM microscopy was first developed in 2000, commercialised in 2007 and rapidly developed. Here we present the changes in capabilities of the SIM microscopes for study of HIV localisation as the instrumentation for structured illumination microscopy has evolved over the past 8 years.

Correlative imaging of fluorescent proteins in resin-embedded plant material.

Fluorescent proteins (FPs) were developed for live-cell imaging and have revolutionized cell biology. However, not all plant tissues are accessible to live imaging using confocal microscopy, necessitating alternative approaches for protein localization. An example is the phloem, a tissue embedded deep within plant organs and sensitive to damage. To facilitate accurate localization of FPs within recalcitrant tissues, we developed a simple method for retaining FPs after resin embedding. This method is based on low-temperature fixation and dehydration, followed by embedding in London Resin White, and avoids the need for cryosections. We show that a palette of FPs can be localized in plant tissues while retaining good structural cell preservation, and that the polymerized block face can be counterstained with cell wall probes. Using this method we have been able to image green fluorescent protein-labeled plasmodesmata to a depth of more than 40 µm beneath the resin surface. Using correlative light and electron microscopy of the phloem, we were able to locate the same FP-labeled sieve elements in semithin and ultrathin sections. Sections were amenable to antibody labeling, and allowed a combination of confocal and superresolution imaging (three-dimensional-structured illumination microscopy) on the same cells. These correlative imaging methods should find several uses in plant cell biology.

Sex-specific analysis of hiking accidents in the Austrian Alps: a follow-up from 2015 to 2021.

Background: Hiking is one of the most popular leisure sport activities practiced in the Alps during the summer season, but bears the risk of mountain emergencies, accidents, and fatalities. This paper provides an updated analysis of hiking accidents for the years 2015 to 2021 in the Austrian Alps, thereby outlining fatal and non-fatal accident characteristics. Methods: For this retrospective analysis, mountain hiking accidents documented by the Austrian Alpine Police during a 7-year period were screened for potential exclusion criteria. The final sample size consisted of 7368 accidents and 7552 victims. The outcome measures were mainly specified by sex, age, injury degree, injury location, pathophysiological characteristics, and cause of injury. Results: The overall annual number of accidents showed a continuous increase from 428 in 2015 to 544 in 2021. In total, 7.1% of the total victims died during the 7-year period, with male hikers being significantly more affected than female hikers (m: 80.8%, f: 19.2%; p ≤ 0.001). The sex specific distribution for non-fatal hiking accidents was 55.9% in women and 44.1% in men. Male victims showed significantly more frequent cardiovascular events (m: 78.5%, f: 21.5%), multiple injuries (m: 60.2%, f: 39.8%), and wounds/blood loss (m: 57.4%, f: 42.6%) than female victims, whereas women showed more fractures (m: 31.5%, f: 68.5%) than men (p ≤ 0.001). Additionally, men were more likely to injure their abdomen/chest (3.7%), head (14.1%), and multiple body parts (26.5%), whereas women were more likely to injure their ankle or foot (42.3%). Finally, men were more likely to have an accident during the ascent (24.1%), whereas women during the descent (69.0%) (p ≤ 0.001). Conclusion: This paper provides the latest data and a deeper insight into sex-specific characteristics of mountain hiking accidents in the Austrian Alps.

Skill-Specific Differences in Equipment-Related Risk Factors for ACL Injury in Male and Female Recreational Skiers.

Background: In recreational alpine skiing, the anterior cruciate ligament (ACL) is affected in approximately 50% of serious knee injuries. There are established sex-based and skill-based differences in ACL injury risk, but the potential impact of equipment used (eg, skis, bindings, and boots) has not been evaluated. Purpose: To evaluate individual and equipment-related risk factors for an ACL injury depending on sex and skill level. Study Design: Case-control study; Level of evidence, 3. Methods: This was a retrospective questionnaire-based, case-control study of female and male skiers with and without ACL injuries during 6 winter seasons (from 2014-2015 to 2019-2020). Demographic data, skill level, equipment specifications, risk-taking behavior, and ownership of ski equipment were recorded. Ski geometry (ski length; sidecut radius; and widths of the tip, waist, and tail) was taken from each participant's ski. The standing heights of the front and back part of the ski binding were measured using a digital sliding caliper, and the standing height ratio was calculated. Abrasion of the ski boot sole was also measured at the toe and heel. Participants were divided by sex into less and more skilled skiers. Results: A total of 1817 recreational skiers participated in this study, of whom 392 (21.6%) sustained an ACL injury. A greater standing height ratio and more abrasion at the toe of the boot sole were associated with increased ACL injury risk in both sexes, independent of the skill level. Riskier behavior increased the injury risk only in male skiers, independent of the skill level, and longer skis increased the injury risk only in less skilled female skiers. Older age, the use of rented/borrowed skis, and more abrasion at the heel of the boot sole were independent risk factors for ACL injury in the more skilled skiers of both sexes. Conclusion: Individual and equipment-related risk factors for an ACL injury partly differed according to skill level and sex. Consideration of the demonstrated equipment-related factors should be implemented in order to reduce ACL injuries in recreational skiers.

Association of personal and equipment-related factors on ACL injury risk in alpine skiers with cautious or risk-taking behaviour: A case-control study.

Background: In recreational alpine skiing ACL injury risk depends on the interaction of individual characteristics and behaviours as well as on equipment-related factors. Aim: to evaluate if and to what extent personal characteristics and equipment-related parameters are associated with ACL injury risk in cautious and risk-taking recreational alpine skiers. Methods: A retrospective questionnaire-based, case-control study of ACL-injured and uninjured in a cohort of cautious as well as risk-taking recreational skiers was conducted. Participants self-reported their demographics, skiing skill level, and risk-taking behaviour. Ski length, side-cut radius, widths of the tip, waist, and tail were recorded from each participant's skis. Standing heights at the front and rear components of the ski binding were measured with a digital sliding caliper, and a standing height ratio between the front and rear components was calculated. Ski boot sole abrasion at the toe and heel pieces was also measured with the digital sliding caliper. Results: In total, 1068 recreational skiers (50.8% females) with a mean age of 37.8 ± 12.3 years participated, of whom 193 (22.0%) sustained an ACL injury, and 330 (30.9%) participants reported a risk-taking behaviour. Results of the multiple logistic regression analyses revealed that a higher age, a lower skill level, a higher standing height ratio, and greater ski boot sole abrasion at the toe as well as heel pieces were independently associated with an increased ACL injury risk in both the cautious and the risk-taking group. Among cautious skiers, a longer ski length was an additional significant risk factor for sustaining an ACL injury. In conclusion, the same personal and equipment related characteristics contribute to an increase in the ACL injury risk regardless of risk-taking behaviour, with the only difference that longer skis represent an additional risk factor in cautious skiers.

Might Gendering Ski Binding Settings be Helpful for the Prevention of ACL Injuries Among Female Recreational Alpine Skiers?

When interpreting sex differences in the injury risk during sport activities, potential gender effects are often overlooked. This might actually be the case with regard to the higher injury risk of the anterior cruciate ligament (ACL) in female skiers. A higher failure rate of ski binding releases has been suggested at least partly to explain the more frequent ACL injuries in female skiers. However, as males seem to be predominantly responsible for the development of standards for ski binding settings, one might speculate that they could rather make standards for males than females. If true, the inclusion of female engineers could actually represent an appropriate approach to reduce ACL injures in female recreational skiers.

Unchanged Fatality Rate on Austrian Ski Slopes during the COVID-19 Lockdown.

Fatalities on ski slopes are very rare, with about one death per one million skier days. Whether the fatality rate is affected by substantial changes in the number of skier days and potentially associated alterations in the structure of the skier population is unknown. Thus, we compared the fatality rate on Austrian ski slopes in the winter season of 2020/21, when skiing activities were dramatically restricted during the COVID-19 lockdown, with those of the previous winter seasons. As a consequence of COVID-19 measures, the number of skier days dropped from over 50 million in previous years to 9.2 million skier days in the winter season of 2020/21. Still, the fatality rate (6.5 deaths/10 million skier days) was not different when compared to any of the seasons from 2011/12 to 2019/20. Despite the lack of international skiers and the reduction in skier days by more than 80%, the fatality rate remained surprisingly unchanged. The weather and snowfall conditions were on average comparable to those of previous winters, and, except for nationality, the composition of the skier population appears to have remained relatively unaltered. In conclusion, the fatality rate during downhill skiing is low and the absolute fatality numbers are primarily a function of the number of skier days.

A Comparison of ACL Injury Risk, Ski Geometry and Standing Height Parameters between Skiers with Rented and with Owned Skis.

AIM: to evaluate if ACL injuries are associated with recreational skiers using rented skis and whether individual factors, ski geometry parameters and standing heights differ between skiers who rented or owned skis. A retrospective questionnaire-based, case-control study of ACL-injured and uninjured recreational skiers was conducted during six winter seasons. Age, sex, body height, body weight, nationality, ownership of skis, skill level, risk-taking behavior, ski length, side-cut radius, widths of the tip, waist, and tail, and the standing heights at the front and rear components of the ski binding were assessed. Additionally, ratios between ski widths and a standing height ratio were calculated. Altogether, 1780 skiers (48.9% females) with a mean age of 39.2 ± 13.0 years participated, of whom 22.0% sustained an ACL injury and 32.3% rented skis. ACL injury risk was significantly associated with rented skis (OR 3.2, 95% CI 2.5-4.0). Compared to skiers using own skis, participants who rented skis were more likely female, smaller and lighter, tourists, less skilled and more cautious. In comparison to owned skis, rented skis showed significantly lower mean values in ski length, side-cut radius, ski widths, and for the three ski widths ratios. Additionally, standing heights were significantly lower while standing height ratio was higher for rented skis. Beside individual factors, equipment-related factors should be considered when renting skis in order to reduce ACL injury risk.

Mortality in Recreational Mountain-Biking in the Austrian Alps: A Retrospective Study over 16 Years.

Despite recreational mountain-biking's growing popularity worldwide, the literature on mortality in this leisure sporting activity is scarce. Therefore, the aim of the present study was to investigate the characteristics of fatal accidents as well as resulting dead victims during recreational mountain-biking in the Austrian Alps over the past 16 years. For this purpose, a retrospective study based on Austrian institutional documentation from 2006 to 2021 was conducted. In total, 97 fatalities (1 woman) with a mean age of 55.6 ± 13.9 years were recorded by the Austrian Alpine Police. Of those, 54.6% died due to a non-traumatic (mostly cardio-vascular) and 41.2% due to a traumatic event. Mountain-bikers fatally accidented for non-traumatic reasons frequently belonged to older age classes (p = 0.05) and mostly (73.6%) died during the ascent, whereas traumatic events mainly (70.0%) happened during the descent (p < 0.001). Throughout the examined period, the absolute number of fatalities slightly increased, whereas the mortality index (proportion of deaths/accidented victims) did not (mean value: 1.34 ± 0.56%). Factors such as male sex in general, above average age and uphill riding for non-traumatic accidents, as well as downhill riding for traumatic events, seem to be associated with fatalities during recreational mountain-biking in the Austrian Alps. These results should be considered for future preventive strategies in recreational mountain-biking.

Improving Spatial Hearing when Wearing Ski Helmets in Order to Increase Safety on Ski Slopes.

This study investigated the effect of a new type of ear pads for ski helmets on the hearing performance of 13 young adults (mean age: 22 years). Free-field hearing thresholds and sound localization performance of the subjects were assessed in three conditions: without helmet, with a conventional helmet and with the modified helmet. Results showed that the modified helmet was superior to the conventional helmet in all respects, but did not allow for a performance level observed without a helmet. Considering the importance of precise hearing and sound localization during alpine skiing, acoustically improved ear pads of ski helmets, as demonstrated in this study, can essentially contribute to enhancing the safety on ski slopes.

Incidences of Fatalities on Austrian Ski Slopes: A 10-Year Analysis.

The study evaluated incidences and potential differences of traumatic and nontraumatic fatalities among recreational skiers and snowboarders on Austrian ski slopes within a 10-year analysis. Within this retrospective study, data were collected by the Federal Ministry of the Interior. Data comprised all traumatic and nontraumatic deaths on Austrian ski slopes which occurred between the 2008/09 and 2017/18 winter seasons. Age, sex, nationality, gear used, altitude, slope difficulty, accident cause, primary cause of death and helmet use were collected at the death scene. Incidence of fatalities was calculated based on number of skier days. In total, 369 fatalities, with an average of 36.9 ± 7.9 fatalities per year, were registered. The yearly incidence of traumatic and nontraumatic deaths decreased by 25.8% and 40.1% during the 10-year time period, leading to an evaluated mean incidence of 0.70 deaths per million skier days, with an incidence of 0.36 traumatic deaths and 0.34 nontraumatic deaths per million skier days. Incidences of both traumatic and nontraumatic deaths decreased during the 10-year analysis, representing death as a rare event on Austrian ski slopes. However, adequate prevention measures to reduce potential risk factors to further reduce the mortality risk on ski slopes are needed.

Negative and positive regulation of gene expression by mouse histone deacetylase 1.

Histone deacetylases (HDACs) catalyze the removal of acetyl groups from core histones. Because of their capacity to induce local condensation of chromatin, HDACs are generally considered repressors of transcription. In this report, we analyzed the role of the class I histone deacetylase HDAC1 as a transcriptional regulator by comparing the expression profiles of wild-type and HDAC1-deficient embryonic stem cells. A specific subset of mouse genes (7%) was deregulated in the absence of HDAC1. We identified several putative tumor suppressors (JunB, Prss11, and Plagl1) and imprinted genes (Igf2, H19, and p57) as novel HDAC1 targets. The majority of HDAC1 target genes showed reduced expression accompanied by recruitment of HDAC1 and local reduction in histone acetylation at regulatory regions. At some target genes, the related deacetylase HDAC2 partially masks the loss of HDAC1. A second group of genes was found to be downregulated in HDAC1-deficient cells, predominantly by additional recruitment of HDAC2 in the absence of HDAC1. Finally, a small set of genes (Gja1, Irf1, and Gbp2) was found to require HDAC activity and recruitment of HDAC1 for their transcriptional activation. Our study reveals a regulatory cross talk between HDAC1 and HDAC2 and a novel function for HDAC1 as a transcriptional coactivator.

The upper limit of cardiorespiratory fitness associated with longevity: an update.

In 2013, mortality reductions with improving cardiorespiratory fitness (CRF) have been suggested to persist until 13 METs. More recently, accumulating evidence from large-scale studies suggests that mortality from all causes decreases with increasing CRF levels, apparently without upper limit of CRF. However, when baseline CRF is assessed in later life, upper limits of CRF decrease depending on the individual fitness level at baseline and the volume and intensity of physical activity performed during follow up. Consequently, both a CRF level as high as possible during early adulthood, achieved by appropriate exercise interventions, and a small CRF decline during later life, by continuation of regular physical activity, will help to optimize longevity.